Biomedical subjects

T H Metzger

Publications and source records attributed to T H Metzger.

4 recordsLinked to original sources

PubMed2003

A focusing crystal analyser for the rejection of inelastic X-ray scattering.

A focusing crystal analyser has been constructed that allows the rejection of inelastic X-ray scattering during diffuse scattering measurements close to an absorption edge. A Johann geometry was obtained by cylindrical bending of perfect silicon and germanium crystals. The choice of reflection, the effect of bending and the contribution of the source size are discussed in relation to the energy resolution. Measurements at the As K-edge (11.867 keV) and at the Cs K-edge (35.985 keV) are presented to demonstrate that the focusing analyser can be used over a wide energy range. A direct comparison with a flat perfect crystal with comparable energy resolution shows a gain in intensity by a factor of 50.

Journal Article↗

PubMed2003

Direct determination of strain and composition profiles in SiGe islands by anomalous x-Ray diffraction at high momentum transfer.

Anomalous x-ray scattering is employed for quantitative measurements of the Ge composition profile in islands on Si(001). The anomalous effect in SiGe is enhanced exploiting the dependence of the complex atomic form factors on the momentum transfer. Comparing the intensity ratios for x-ray energies below and close to the K edge of Ge at various Bragg reflections in the grazing incidence diffraction setup, the sensitivity for the Ge profile is considerably enhanced. The method is demonstrated for SiGe dome-shaped islands grown on Si(001). It is found that the composition inside the island changes rather abruptly, whereas the lattice parameter relaxes continuously.

Journal Article↗

PubMed2003

Pure silica BETA colloidal zeolite assembled in thin films.

Pure silica nanoscale zeolite BETA with monomodal particle size distribution was synthesized from a colloidal precursor solution and successfully applied for the preparation of hydrophobic ultrathin films on silicon wafers via spin coating.

Journal Article↗

PubMed2002

X-ray diffraction from rectangular slits.

It is shown that for micrometre-sized beams the X-ray diffraction from slits is a source of strong parasitic background, even for slits of high quality. In order to illustrate this effect, the coherent diffraction from rectangular slits has been studied in detail. A large number of interference fringes with strong visibility have been observed using a single set of slits made of polished cylinders. For very small apertures, asymmetrical slits generate asymmetrical patterns. This pattern is calculated from the theory of electromagnetic field propagation and compared with experiment in the far-field regime. The use of guard slits to remove Fraunhofer diffraction from the beam-defining slits is treated theoretically. Numerical simulations yield the optimum aperture of the guard slits with respect to the distance to the primary slits. Diffraction theory is shown to be essential to understand how to reduce the background-to-signal ratio in high-resolution experiments.

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